1. Field of the Invention
The present invention relates to segments of a spliced prestressed concrete girder and a method of manufacturing the segments, and more particularly, to segments of a spliced prestressed concrete girder, which have improved structural integrity at joints, and a method of manufacturing the segments.
2. Description of the Related Art
A spliced prestressed concrete girder is an integral type prestressed concrete girder which is manufactured as a plurality of segments and then transported to a construction site where the segments are connected to one another and tendons are tensioned in the girder a longitudinal direction thereof.
The segments of the spliced prestressed concrete girders can be connected by a cast-in-place method of placing the segments at the construction site at predetermined intervals, splicing reinforcing bars, and casting concrete, mortar, or grout around the reinforcing bars. A method of thinly coating an adhesive, such as epoxy, over joint surfaces of the segments, or a method of securing the segments using only the tensile force of the tendons without any adhesive are other methods for connecting the segments.
The cast-in-place method wherein concrete, mortar, or grout is cast at joints has an advantage in that the segments which are to be connected do not need to have the mating cross-sections, but has disadvantages of complex construction process and long construction cycle because the reinforcing bars should be placed between the segments and concrete, mortar, or grout should be cast and cured.
The method of securing the segments using the tensile force of the tendons with or without epoxy can significantly reduce construction cycle time and incur low costs, compared to the cast-in-place method, since as shown in FIGS. 1 and 2, a girder 9 is built by connecting prefabricated segments 1 using joints with shear keys 2. However, the method of securing the segments using the tensile force of the tendons has a drawback in that the segments 1 to be connected should have the precisely mating cross-sections. Also, it is difficult to fabricate the segments 1 because corresponding concave-convex portions of the shear keys between the connected segments 1 should be mated completely or within a thin adhesive thickness range despite the fact that the joints of the segments 1 have complex shapes due to the shear keys 2, guide keys, tendon ducts, and so on. In addition, the girder 9 is structurally weak because longitudinal reinforcing bars are discrete at the joints and stress concentration at joints may happen due to a manufacturing error or improper epoxy preparation or application.
Also, since existing formworks in which the segments 1 are made are expensive, the lengths of the segments have been standardized and only girders or segments having the standard lengths have been manufactured, thereby making it difficult to manufacture segments or girders of various lengths.